1. Field of the Invention
The present invention relates to a process for the recycling of dry batteries or batteries containing cadmium, zinc, lead or alkali metals using pyrolitic methods, wherein the batteries may be unsorted and be present in shredded or unshredded form. The invention also relates to installations for performing the recycling process.
2. Description of the Prior Art
A large number of processes for recycling batteries are known in which however the batteries must be sorted according to their composition and in which the individual process is suitable for one type of battery only. This is especially true for the known process of the S. N. A. M. company in Lyon, which is suitable only for the processing of Ni--Cd accumulators. Further examples of processes for the recycling of sorted batteries, e.g. used alkali-manganese and zinc-carbon batteries, have e.g. become known from the Japanese patents JP-A-74/106,519 and JP-A-75/60,414. Therein it is proposed to scrap the corresponding batteries, to treat them with hydrochloric acid, and to separate out manganese from the solution as hydroxide by neutralizing with NH.sub.4 OH at pH 5, and as Mn.sub.2 O.sub.3 at pH 9 after addition of MnO.sub.2 or H.sub.2 O.sub.2. In accordance with U.S. Pat. No. 3,438,878 zinc and manganese dioxide are to be won simultaneously in the electrolysis of a solution containing sulphuric acid. All these processes, which use sorted batteries as raw material, are unable to succeed simply because the number of batteries returned is relatively small and always requires subsequent sorting. This means that the intake area for a given installation is so large that the costs of collection are much too high. Various processes have become known which improve the sorting process, which processes follow a separation according to chemical or geometric criteria. The rejected quantity, however, still remains as a critical waste product.
An intermediate step is represented by certain processes which are restricted to reducing the toxicity of waste containing mercury, in which the batteries are taken in unsorted. One example is the process of the Vost company in which the mechanically crushed batteries have their mercury content removed in a vacuum at temperatures of about 400.degree. C. A similar principle was put into operation in the Clean Japan Center by Mitsui Metals Co. and Nomura Kosan Co. This method, which is known as the CJC process, works in such a manner that the batteries are first freed from their metal cases and then thermally treated in two stages at temperatures of 600.degree. C. -800.degree. C.
The most recent processes are those in which unsorted batteries are recycled. One solution is described e.g. by EP-A-150,821 of the Metallgesellschaft AG. Here, the small batteries are first mechanically crushed and certain additives added, whereupon this product is subjected to a chloridizing roasting at a temperature from 580.degree. C. to 700.degree. C. The vaporized mercury is washed out of the exhaust gas. The product of roasting is then treated with dilute hydrochloric acid and the nobler metals then precipitated out of the solution by cementation with zinc. Sumitomo Heavy Industries Ltd. has developed a pyrometallurgical method for processing unsorted batteries. This process provides that the battery scrap be put into a cupola furnace and then run through three successive stages, namely an oxidation stage for distilling off the mercury, a subsequent reduction stage for vaporizing the zinc, and finally a high temperature melting zone in which the entire remaining residue is processed to a fused product. Due to the direct succession of thermal treatment zones in the cupola furnace, certain problems relating to the development of dioxins and PCBs have been observed. Due to the unpredictability of the composition of the furnace charge, the temperature control is extremely difficult to manage. A corresponding test installation in Switzerland burned through. The problems were later eliminated.
Further, there is a process (CH-A 04 969/86-0) which in the mean time has yielded positive results even in continuous operation. In this process, the unsorted batteries are first subjected to a pyrolysis stage in which the organic constituents are burned and the water and mercury are vaporized off. The product of pyrolysis is then shredded and washed, whereupon after addition of HBF.sub.4 a solution results which can be separated by means of electrolysis into various relatively very pure metal fractions. In an improved version (WO 93/20593) a second pyrolysis is now performed after the first pyrolysis and the subsequent shredding.
All known processes in which unsorted batteries are recycled have the goal of separating the resulting mixture as far as possible into different fractions which are as pure as possible. None of the known processes with the exception of the last named process of the Recyctec SA company have ever reached the commercial phase. These processes can exist commercially only when the take-back price of the unsorted batteries is high. This prerequisite is compelling since the costs of the installation are enormous.